Breast cancer and synchronous multiple primary lung adenocarcinomas with heterogeneous mutations: a case report

Multiple primary malignant tumors (MPMT) refers to the presence of two or more primary cancers of different organs in the same patient. MPMT is a sparse disease in the past, but there has been a gradual increase in the morbidity. Since multiple primary malignant tumors treatment methods differ, it is essential for clinicians to be able to distinguish between separate primary lesions and metastasis. We present the case of a 57-year-old woman with MPMT presenting with cancer in the left breast and synchronous double primary lung adenocarcinomas. We used IHC and epidermal growth factor receptor(EGFR)mutation to analyze genomic alteration profiles in the patient to validate the difference among the pathological assessments and the clinical differences between double primary lesions of lung and breast. EGFR gene analysis of breast cancer lesion revealed no mutations. The left and right lower lobe lung adenocarcinomas contained EGFR gene mutations: an L858R point mutation in exon 21 in the left lesion and a deletion mutation in exon 19 in the right lesion. The breast cancer and both lung adenocarcinomas were surgically resected. To date, the patient has remained disease-free. Both pathological and molecular assessment adapted in the current study appeared necessary. Mutational analysis of the EGFR gene provided important information not only in the diagnosis and but also in the treatment of MPMT.